Tracking devices used especially for welding random seams are known and usually utilize mirrors or television cameras to scan the seam and thus maintain the welding device over the seam. However, these devices suffer from significant drawbacks that limit their speed and accuracy. Cameras using CCD arrays or Vidicons have speed and resolution limitations. These limitations stem from the lack of random access of the information on the CCD array and the time required for sufficient exposure of the camera. Mechanically scanned mirrors have inertial constraints that also do not allow random access scanning. This failing frustrates the system designer's need to randomly move the scan in order to maximize exposure and minimize data collection time.
Thus, the number of scans across a seam during a specific period of time is limited. Accordingly, the accuracy of the seam tracking is likewise limited, thereby restricting the speed at which the welding machine can move longitudinally of the seam.
Examples of the known prior art relating to tracking systems and scanners are disclosed in the following U.S. Patents: U.S. Pat. No. 3,135,857 to Von Voros; U.S. Pat. No. 3,370,151 to Normando; U.S. Pat. No. 3,757,125 to Okada et al; U.S. Pat. No. 4,218,142 to Kryger et al; U.S. Pat. No. 4,300,836 to Holmes et al; U.S. Pat. No. 4,328,416 to Dudley et al; U.S. Pat. No. 4,380,700 to Kallen; U.S. Pat. No. 4,417,127 to Nachev et al; and U.S. Pat. No. 4,427,880 to Kanade et al.